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WHYWhy does…? · #20EP.214 · 24 s

Why does…? #20: why LED lights flicker on your phone camera

Cover of the lesson: Why does…? #20: why LED lights flicker on your phone cameraComing to YouTube soon
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// WHAT YOU WILL LEARN

Many LED lamps blink 100 or 120 times a second with the mains (or with PWM dimming); your eye blends it, but a fast camera shutter catches the dark moments as bands.

// LESSON NOTES

Filmed a lamp and saw dark stripes rolling across it? Here's why! 💡📱

⚡ Mains power flips direction 50 times a second (230 V · 50 Hz: India, UK, Europe) or 60 times (120 V · 60 Hz: USA, Canada).
💡 So many LED lamps dip in brightness twice per flip: 100 times a second (120 in the USA).
👀 Way too fast for your eyes — they blend it into steady light.
📸 But most phone cameras read the picture row by row, top to bottom. Rows read during a dark moment come out darker = dark stripes!
🔧 Tip: try a slower shutter (1/50 or 1/100 s) or anti-flicker mode — good LED lamps barely flicker.

Read the voiceover (transcript)
  1. Filmed a lamp and saw dark stripes? Here's why!
  2. Mains power flips fifty or sixty times a second.
  3. So many LED lamps flicker a hundred times a second.
  4. Too fast for your eyes. They blend it into steady light.
  5. So why does the camera see it?
  6. It reads the picture row by row!
  7. Dark moments become dark stripes!
  8. Next: why a power bank drains by itself. Follow for more!

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